Comorbid cocaine dependence among methadone maintained patients interferes with treatment outcomes. Prazosin (alphai-adrenergic antagonist) and DpH inhibition (disulfiram) have shown promising results in the treatment of cocaine dependence. While inhibition of DpH activity is hypothesized to increase dopamine (DA) but decrease norepinephrine neurotransmission and to intensify the dysphoric experience of cocaine use, the selective inhibition of alphai-adrenergic receptor antagonist is hypothesized to attenuate DA neurotransmission primarily in the nucleus accumbens and to reduce the reinforcing effects of cocaine use. The objective of this proposal is to determine to what extend does prospective screening for a functional polymorphism of dopamine beta hydroxylase (DBH-1021CvT) or polymorphisms in the promoter region and the coding region ofthe alpha-la-adrenoceptor receptor gene (ADRAIA) predict the treatment efficacy of nepicastat (a new DpH inhibitor) or prazosin among newly admitted methadone treated patients. Based on our previous studies, we hypothesize that carriers ofthe low-OpH associated T allele will have significant reductions in cocaine use, because they are more susceptible to inhibition of DpH by nepicastat. We also will assess post-hoc the impact of functional variants ofthe ADRAIA on the response to prazosin. This 12- week double-blind, placebo controlled randomized clinical trial will provide treatment for 150 cocainedependent opioid dependent patients who have 2-weeks of methadone induction and 4 week discontinuation for 18-weeks total. Participants, aged 18-65 years, will be randomized to receive prazosin 10 mg/day, nepicastat 120mg/day, or placebo while concurrently receiving treatment with methadone. All participants receive weekly 1-hour psychotherapy (Cognitive Behavioral Treatment). The primary outcomes will be reduction in opioid and cocaine use, as assessed by self-report and confirmed by thrice-weekly urinalyses. The proposed study is expected to provide a better understanding ofthe role ofthe DpH inhibitor nepicastat and the selective alphaiA adrenergic receptor antagonist prazosin on cocaine using behavior among distinct DBH -1021C-+T genotypes or the functional variants in the promoter and coding region of ADRA1A.